The use of Bpa pa reference point when determining TAC for the north north-east arctic cod ( Gadus morhua L.): how valid is it? (861.2Kb)

The 11th Russian-Norwegian Symposium

Ecosystem dynamics and optimal long term harvest in the Barents sea fisheries

The use of

The use of B B

reference point when reference point when determining TAC for the north

determining TAC for the north - - east arctic east arctic cod (

cod ( Gadus Gadus morhua morhua L.): how valid is it? L.): how valid is it?

V. M.

V. M. BorisovBorisov

Federal Research Institute of Fisheries and Oceanography Federal Research Institute of Fisheries and Oceanography (VNIRO), Moscow, Russia (VNIRO), Moscow, Russia

TAC TAC

establishment establishment

next questions:

●● Do the species examined meet the rule: Do the species examined meet the rule:

SSB ≥

SSB ≥ BB_papa= ensures strong R? = ensures strong R? (SSB (SSB –– spawning spawning stock biomass;

stock biomass; BB_papa –– precautionary approach SSB; R precautionary approach SSB; R –– fishing recruitmentfishing recruitment))

●● Are the search and application of Are the search and application of BB_papa justified justified in case of species with poor or statistically in case of species with poor or statistically

uncertain SSB

uncertain SSB →→R relationship?R relationship?

Materials

●● AFWG data of SSB and NAFWG data of SSB and N_{3 3} of NEAcodof NEAcod (1946(1946-2005)-2005)

●● Weights and the survival ratio for each age groupWeights and the survival ratio for each age group

Methods

●● Correlation between SSB and NCorrelation between SSB and N₃₃

●● Variance analysis Variance analysis –– the share of the SSB effect on the share of the SSB effect on formation of recruitment against the background of formation of recruitment against the background of

other factors other factors

●● CheckCheck-up of survival effect of 3-up of survival effect of 3--5 age groups on 5 age groups on the fishing stock

the fishing stock

R e s u l t s

Correlative coefficient for 56 pairs of Correlative coefficient for 56 pairs of

SSB SSB – – N N

(r = 0.23) is statistically (r = 0.23) is statistically insignificant

insignificant

Table 1. Estimation of the SSB role in forming of the cod recruitment (N³) (data of one way variance analysis)

between groups

inside

groups total mSa mSe

(r) (n) (SSa) (SSe) (SS) SSa/SSx100% (Fc) (Fs)

< 600 0.13 47

> 600 -0.37 ⁹

< 400 0.16 39

401-800 0.31 13 361173 7569015 7930188 4.55 180586.6 145558.0 1.24065 3.17515

> 800 -0.17 4

< 250 0.44 23

251-500 0.24 20

501-750 0.32 9

> 750 -0.17 4

< 300 0.32 26

301-600 -0.03 21

601-900 -0.42 6

> 900 -0.73 ³

< 250 0.44 23

251-500 0.24 20

501-750 0.32 9 350802 7579386 7930188 4.42 87700.5 151587.7 0.57855 2.55718

751-1000 - 1

> 1000 -0.73 3

< 200 0.46 16

201-400 -0.29 23

401-600 -0.01 8

601-800 -0.35 5

801-1000 - 1

> 1000 -0.73 3

Common 0.23 ⁵⁶

233324.8 138031.9 1.69037 2.40438 1166624 6763564 7930188 14.71

221917.5 142439.9 1.55797 2.78623 665753 7264435 7930188 8.40

114612.3 148752.0 0.77049 2.78623 343837 7586351 7930188 4.34

Fisher's standart criterion

598553 7331635 7930188 7.55 ^{598553.4 138332.7 4.32691* 4.02301}

SSB groups

Correl. coef.

by groups

Generations in group

Sum of devations' square

SSB role for N3

Average sums of Fisher's calculat.

criterion

Comments: SSa - factor mutability (for studied factor); SSe - variate mutability;

SS - total mutability; mSa - deviation of group averages of studied factor;

mSe - deviation of group averages of nonstudied factors; Fc = mSa/mSe; Fs for Р=0.95;

blue figures are statistically significant;

* - Fc>Fs indicates the confidence of the effect of the factor considered

Fig. 1. Strength of the year-classes (N3) born from different SSB levels. Figures in the rectangles point quantity /percentage of the year-classes by N3 groups in every SSB range. Shaded rectangles show the zone of correspondence among N3 and SSB range.

300 600

0 900 1200

SSB x 10³t 3(13.6%)

1(20%) 1(33.3%)

1(33.3%) 900

1200 1500 1800

N 3x 106 ind. _{5(19.2%) 1(4.5%)}

2(40%) 2(40%)

500

5(19.2%) 5(22.7%)

600 5(19.2%) 13(59.1%)

11(42.4%) 300

1(33.3%)

0 200 400 600 800 1000 1200

SSB, 103 t

0 150 300 450 600 750

PF, 1012 eggs

а ^{r = 0,86}

0 200 400 600 800 1000 1200

1946 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

years SSB, 103 t

0 200 400 600 800 1000 1200

Pel.Y, ind./mile2

b r = 0,8

Fig.2. NEAcod. Spawning stock biomass (SSB), population fecandity (PF) and pelagic young (Pel.Y.) (-●- SSB; -♦- PF; -■- Pel.Y.)

a

0 200 400 600 800 1000 1200 1400 1600

SSB, 103 t

0 10 20 30 40 50 60 70 80

ind./hour trawl

r = 0,05

а

0 200 400 600 800 1000 1200 1400 1600

SSB, 103 t

0 10 20 30 40 50 60 70 80

ind./hour trawl

r = 0,08

b

0 200 400 600 800 1000 1200 1400 1600

1946 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

years SSB, 103 t

0 10 20 30 40 50 60 70 80

ind./hour trawl

r = 0,08

c

Fig.3. NEAcod. Spawning stock biomass and relative abundance of the benthonic young of age “0+”(--♦♦--); “1+”(-■-); “2+”(-▲-)

0 10 20 30 40 50 60 70 80

1946 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

ind./hour trawl

Fig.4. NEAcod. Relationship between relative abundance of the benthonic young at age “0+”(--♦♦-); “1+”(-■-); “2+”(-- ▲-)

r between:

“0+” and “1+”=0,46

“1+” and “2+”=0,77

“2+” and “0+”=0,61

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

3 4 5 6 7 8 9 10 11 12 13 14 15

age

surv. coefficient (S)

0 4 8 12 16 20 24 28

weight, kg

Fig.5. NEAcod. Survival coefficients (—) and weights (—) at age 3-15

Table 2. Change in the fishing stock biomass (FSB) at different survival levels in 3-5-age cod

Age Weight,

kg S₁ N1 ·10³ ind.

FSВ1

10³t S₂ N2 ·10³ ind.

FSB2

10³t S₃ N3 ·10³ ind.

FSB3

10³t 3 0.27 0.657 500000 135000 0.700 500000 135000 0.800 500000 135000 4 0.69 0.655 328500 226665 0.700 350000 241500 0.800 400000 276000 5 1.35 0.547 215167 290475 0.600 245000 330750 0.700 320000 432000 6 2.28 0.443 117700 268356 0.443 147000 335160 0.443 224000 510720 7 3.47 0.375 52140 180926 0.375 65121 225970 0.375 99232 344335 8 4.93 0.321 19552 96391 0.321 24420 120391 0.321 37212 183455 9 6.63 0.314 6276 41610 0.314 7839 51973 0.314 11945 79195 10 8.55 0.289 1971 16852 0.289 2461 21041 0.289 3751 32071 11 10.67 0.270 569 6071 0.270 711 7586 0.270 1084 11566 12 12.96 0.250 154 1996 0.250 192 2488 0.250 293 3797

13 15.39 0.230 38 585 0.230 48 765 0.230 73 1123

14 17.95 0.210 9 161 0.210 11 197 0.210 17 305

15 20.59 2 41 2 41 3 62

Sums FSВi 1265 1473 2010

Difference between sums: FSВ2-FSВ1=208000 t FSВ3-FSВ2=537000 t FSВ3-FSВ1=745000 t

Discussion

●● BB_papa’s’s reputation as a biological reference point reputation as a biological reference point for fisheries management is unreasonably high for fisheries management is unreasonably high

●● As for cod, As for cod, BB_papa sustains only population sustains only population

fecundity and pelagic young abundance but it fecundity and pelagic young abundance but it

is not always true for N is not always true for N₃₃

●● Starting from the formula Starting from the formula BB_papa = = BB_limlim exp (1.645 s) exp (1.645 s) BB_papa is rather a statistical than biological indexis rather a statistical than biological index

MAIN ELEMENTS OF TAC SETTING MAIN ELEMENTS OF TAC SETTING

Analysis of previous and current status of the stock:

assessment of fishing stocks (S), relative interannual changes (∆S%);

Influence of S on recruitment (R_s), growth (W_s), natural mortality (M_s)

Analysis of previous and current status of fisheries:

catches (C), relative interannual changes (∆C%);

assessment of CPUE, F, correspondence of ∆C% with ∆S%, influence of C on S

Forecast S _i+1 = S – C – M_s + R_s + W_s,

where R_s prognosis is based on surveys of young fish and assessment of conditions of its survival on the stages from eggs to R_s; M_s includes cannibalism,

discards, and other accountable losses of S

Assessment of ∆S _{i + 1}% based on S – S _i+1

Choice of reasonable ∆C _i+1%

based on ∆S _i+1%, tendencies in S and CPUE assessments, and consideration of W_s and M_s trends

Setting of TAC_i+1

based on ∆S _i and chosen ∆C _i+1%

Conclusion

●● Common use of the BCommon use of the B_papa at TAC setting is not at TAC setting is not always reasonable

always reasonable

●● BB_papa estimation cannot be regarded as properly estimation cannot be regarded as properly biologically based in the case of species with biologically based in the case of species with

R dependent on survival conditions for pre R dependent on survival conditions for pre--

fishery young to a greater extend than SSB fishery young to a greater extend than SSB

●● It would be reasonable to check the SSB effect It would be reasonable to check the SSB effect on the R formation prior to determining

on the R formation prior to determining BB_papa and and using it for TAC setting

using it for TAC setting

…and are you sure the key to TAC was lost just here?

- Most likely

there. But here is lighter place...